Calculating the Astronomical Unit (AU), Astronomers observed the Venus transit from various places. Because of the parallax effect, observers like A and B saw Venus's path shifted on the Sun's face. By trigonometry, this shift & the distance between the observers you can determine the distance to Venus. It's about 0.35 AU, so knowing the distance in miles, you can get the length of the AU in miles. Mona Evans, "Transit of Venus - Measuring the Solar System" http://www.bellaonline.com/articles

Calculating the Astronomical Unit (AU), the Earth-Sun distance. Astronomers observed the Venus transit from many different places. Because of the parallax effect, observers like A and B saw Venus's path shifted on the Sun's face. By trigonometry, this shift, plus the distance between the observers, you can determine the distance to Venus. In terms of the Astronomical Unit the distance is about 0.35 AU. Knowing the parallax distance in miles, you can determine the length of the AU in miles.

Calculating the Astronomical Unit (AU), Astronomers observed the Venus transit from various places. Because of the parallax effect, observers like A and B saw Venus's path shifted on the Sun's face. By trigonometry, this shift & the distance between the observers you can determine the distance to Venus. It's about 0.35 AU, so knowing the distance in miles, you can get the length of the AU in miles. Mona Evans, "Transit of Venus - Measuring the Solar System" http://www.bellaonline.com/articles

Calculating the Astronomical Unit (AU), the Earth-Sun distance. Astronomers observed the Venus transit from many different places. Because of the parallax effect, observers like A and B saw Venus's path shifted on the Sun's face. By trigonometry, this shift, plus the distance between the observers, you can determine the distance to Venus. In terms of the Astronomical Unit the distance is about 0.35 AU. Knowing the parallax distance in miles, you can determine the length of the AU in miles.